revert #652

reverting broad cosmetic/style change because:
- increases merge-conflicts
- increases overhead of merging upstream Vim patches
- reasons for change are ambiguous, so default to no change

src/msgpack_rpc.c

@@ -93,7 +93,7 @@ char *msgpack_rpc_raw_argument(msgpack_object *obj)
 {
   char *rv = xmalloc(obj->via.raw.size + 1);
   memcpy(rv, obj->via.raw.ptr, obj->via.raw.size);
-  rv[obj->via.raw.size] = '\0';
+  rv[obj->via.raw.size] = NUL;
 
   return rv;
 }